1. Field of the Invention
The present invention relates to an electric hammer, and more particularly, to a technique of reducing and alleviating vibration in an electric hammer that drives a hammer bit at a predetermined cycle, such as a hammer and a hammer drill.
2. Description of the Related Art
Japanese unexamined laid-open Utility Model Publication No. 51-6583 discloses a hammer with a vibration reducing device. According to the known hammer, a counter weight is provided on a crank arm mechanism and driven by the crank arm mechanism. The crank arm mechanism is designed to reciprocate the striker that applies a striking force to the hammer bit. The counter weight reciprocates within a gear housing in a direction opposite to the direction of the striker being driven by the crank arm mechanism. Such movement of the counter weight in the opposite direction can effectively reduce and alleviate vibration in the axial direction of the hammer bit during the operation of the hammer.
Such a counter weight requires considerable dimensions in order to appropriately reduce strong vibration during the operation of the hammer. Accordingly, the space for receiving such a dynamic vibration reducer also requires considerable spaces within the hammer. Further, in some cases, no need does exist to mount the counter weight in the hammer, depending on the operating conditions, user needs, etc. Therefore, a further improvement is desired in the rational design of the counter weight in the electric hammer.